1. Technical Field
The present invention relates to a low-luminance imaging device using a silicon photomultiplier.
2. Description of the Related Art
Conventional night imaging devices, which are mainly exemplified by a security camera, are of the infrared (IR) light emitting diode type that observes reflected IR scanning rays using a low-luminance pickup device including an IR lens coating or an iris lens, and are frequently employed in short-distance observation because of the limitations of observation distance or image quality.
However, the conventional imaging device using the light emitting diode is disadvantageous in terms of observation at low luminance, thus making it difficult to identify a distant subject, and is also problematic in that its size is difficult to reduce and power consumption is high because of the output of the IR light emitting diode.
In addition to the conventional night imaging device, a pickup device including a photomultiplier tube (PMT) for multiplying the number of photons and a lens combined thereto is being used as a low-luminance imaging device.
In the configuration of such a conventional low-luminance imaging device, the PMT is typically exemplified by a microchannel plate (MCP)-PMT similar in shape and principle to a vacuum tube type PMT.
The MCP-PMT, having a honeycombed shape, allows electrons to collide with the inner walls while passing through millions of optical fiber bundles thus emitting secondary electrons. Generally, the final multiplication factor of the electrons passed through the inner walls amounts to about 104 times.
However, the conventional MCP-PMT is disadvantageous because it has a large volume, requires a high voltage of at least 1 kV, and is comparatively expensive.
Furthermore, because the MCP-PMT is affected by a magnetic field, it cannot be applied to equipment using a large magnetic field such as a magnetic resonance imaging device.